This invention relates to apparatus for delimbing felled trees. More particularly, the delimbing apparatus of interest removes limbs by impact shearing as a tree is pulled horizontally through the apparatus.
Many of the tree delimbers shown in the art are designed to handle large trees and are, therefore, of heavy construction and relatively mechanically complex. Other delimbers, of lighter construction but of no less complexity, are designed as articulated attachments to a skidder or bucket loader, usually in combination with a set of shear blades for severing the tree. Characteristic of both types of delimbers are a pair of arcuate arms that enclose the outer portion, with respect to the delimber, of the tree and hold the tree into contact with a set of secondary blades that encloses the under portion of the tree. The arcuate arms are typically engaged by a hydraulic jack system actuated from the cab of the prime mover. Secondary blades are often flexible and spring supported. These are engaged as the arms pull the tree into contact with the delimber frame. Typical delimbers of the type discussed above are shown in Moser, U.S. Pat. No. 3,842,872 and in McCabe U.S. Pat. No. 3,809,134.
To simplify or eliminate the relatively complex hydraulic systems typically used to urge the arcuate arm blades into contact with a tree, various approaches utilizing the weight of the blade or tree to ensure adequate blade-tree contact have been tried. For example, in Jouppi, U.S. Pat. No. 3,881,532, a tree, as it is pulled horizontally through the delimber, contacts a depresser plate which, acting through a rod, lever and pulley system, releases a safety catch and activates a pusher bar causing a mast, upon which is mounted a flexible upper blade, to pivot downward and contact the upper half circumference of the tree. The weight of the blade system ensures that the blade remains in contact with the tree as it is pulled through the delimber. A separate mechanism is provided to raise the mast-blade system after the tree is pulled free of the delimber. In Nadeau, U.S. Pat. No. 3,868,981, an upper blade and a lower blade are interconnected through a rigid arm such that the weight of a tree as it is pulled horizontally through the delimber, contacting the lower blade, is transmitted to the upper blade causing the upper blade to engage the tree. The weight of the tree ensures that both blades are in continual engagement until the tree is pulled free of the apparatus.